Method and apparatus for nondestructive testing of physical characteristics of a specimen using ultrasonic waves

ABSTRACT

The sound velocity (V) in a cast specimen is measured with ultrasonic wave and the sound velocity ratio (V/Vm) between the sound velocity in said specimen and the sound velocity (Vm) in a specified metal corresponding to said specimen is attained; by converting this sound velocity ratio to a physical quantity to be determined (e.g., percent spheroidicity of graphite, state classification, tensile strength or percent elongation) in accordance with an empirical formula (530) or the like which relate to the sound velocity ratio, a physical characteristic value related to said specimen is computed. As a result, values of analysis on the state of castings structure and their characteristic values can be measured or computed with high probability in a nondestructive and convenient manner.

TECHNICAL FIELD

This invention relates to a method and an apparatus for ultrasonicmeasurement. More particularly, this invention relates to a method bywhich the values of physical characteristics such as tensile strength,percent elongation, and the percent spheroidicity of graphite, as wellas the values of state analysis, can be measured or calculated oncastings such as gray cast iron, CV cast iron, and spheroidal graphitecast iron by ultrasonic waves in a nondestructive manner. The inventionalso relates to an apparatus for implementing the method for ultrasonicmeasurement.

BACKGROUND ART

Both the manufacturer and the user of a machine part generally haveserious concerns as to whether that part is truly made of a material tospecifications. This is because the use of an incorrect or defectivematerial has high potential to lead directly to a disastrous accidentdue to failure of the part.

Therefore, the manufacturer makes it a rule to conduct materials testson each of the parts produced, and guarantees the authenticity of anindividual part by issuing a materials test performance list whichcertifies that it has been produced from the material to specifications.In the case of cast iron products, the materials tests to be conductedinclude a tensile test and a hardness test. As for spheroidal graphiteiron products, an additional test is conducted to determine the percentspheroidicity of graphite.

While this is generally the basic way adopted to certify theauthenticity of materials, materials tests require about three or fourdays including the processing of test pieces and other steps, so themanufacturer has desired the development of a method that enablesvarious materials characteristics to be estimated in a simpler andquicker way.

On the side of the user, a need exists for verifying on the actualsample that the part of interest is truly made of the material tospecifications. However, to prepare a test piece for materials testing,the actual sample must be broken, and it has been desired to develop amethod by which tensile strength and other properties can satisfactorilybe estimated in a nondestructive manner.

As for the test to estimate the percent spheroidicity of graphite inspheroidal cast irons to be evaluated by various materials tests, anapparatus for ultrasonic measurement was developed in the early eightiesthat was capable of indirect determination of the percent spheroidicityof graphite using the fact that the velocity of sound (the term "soundvelocity" as used herein means the speed of propagation of ultrasonicwaves) varied with the shape of graphite particles.

A block diagram of an apparatus that measures the sound velocity on acast specimen by ultrasonic wave and which computes automatically thepercent spheroidicity of graphite in the specimen is shown in FIG. 16.

In the drawing, numeral 1 designates an ultrasonic probe, 2 is anultrasonic flaw detector, 3 is a D/A converter circuit, 4 is a bus line,5 is a ROM, 6 is a RAM, 7 is a keyboard (KBD), 8 is a CRT, and 9 is amicroprocessor (MPU). Details of interface circuits and the like thatare connected between these components are omitted from FIG. 16.

Further referring to FIG. 16, numeral 51 designates a program formeasuring the sound velocity, 52 is a program for computing the percentspheroidicity, 53p is a V-S conversion formula, and 54p is a mainprogram; these programs are stored in ROM 5 and executed by MPU 9 toperform the functions they are assigned respectively.

Sound velocity measuring program 51 is activated by main program 54pwhen it is instructed to start measurement via keyboard 7, and theultrasonic flaw detector 2 is controlled via bus line 4 to measure thesound velocity on the specimen 1a. Stated more specifically, theultrasonic wave sent from the ultrasonic probe 1 is partly reflected bythe surface of the specimen 1a, whereas the remainder propagates throughthe interior of the specimen 1a and is also reflected by its bottom.These reflected waves are detected with the ultrasonic probe 1 and uponreceiving the detection signal, the ultrasonic flaw detector 2 measuresthe time from the point of detection of the surface reflected wave tothe point of detection of the bottom reflected wave. The measured timeis sent to the D/A converter circuit 3 and thence delivered to MPU 9 asa digital value. The delivered time is the time taken by the ultrasonicwave to go back and forth through the specimen 1a and, hence, the inputdigital value is divided by twice the thickness of the specimen 1a thatis preliminarily measured and which has already been entered from thekeyboard 7 and, as a result of this operation, the sound velocity on thespecimen 1a is determined.

The thus-measured value of sound velocity is stored in area V in RAM 6by means of the sound velocity measuring program 51.

The program 52 for computing the percent spheroidicity is subsequentlyactivated by the main program 54p and performs a conversion process inaccordance with the V-S conversion formula 53p, thereby computing thepercent spheroidicity of graphite from the value of sound velocitystored in area V. The computed percent spheroidicity of graphite isstored in area S in RAM 6.

The V-S conversion formula 53p represents the relationship between thesound velocity and the percent spheroidicity of graphite for castings,and is an empirically determined conversion formula. Statedspecifically, this is a regression line as constructed by plotting theresults of measurement on a plurality of castings in relevant positionson a coordinate system, the horizontal axis of which may typicallyrepresent the sound velocity (V) as determined by ultrasonic measurementwhile the vertical axis represents the percent spheroidicity of graphite(S) as determined by direct means of measurement in accordance with theJIS (Japanese Industrial Standards) (see 53a in FIG. 17).

The percent spheroidicity of graphite stored in area S which has beencomputed on the basis of this empirical formula is displayed on CRT 8 bythe main program 54p as the result of measurement.

The tensile strength of castings is measured directly by a so-called"tensile test", or a test in which the load or the like that is appliedwhen a test piece worked to a prescribed shape breaks is measured on acalibrated tensile tester.

However, the tensile test takes time in preparing test pieces, workingthem, conducting the test, etc. and, hence, three or four days arenecessary before the inspector knows the acceptability of the materialbeing tested. Under the circumstances, there has been a need for amethod by which the tensile strength of a cast product can be known assoon as it is produced, and which enables one to be sure that the castproduct has been definitely yielded from the material to specifications.

The tensile strength of a cast product depends on the tensile strengthof its base and the shape of fine graphite grains that are distributedin the base and, hence, the tensile strength of the cast product wouldbe estimated by combining its hardness, which is a substitute value ofthe tensile strength of the base, with the percent spheroidicity ofgraphite which indicates the shape of graphite. On the basis of thisidea, a method has been proposed that determines indirectly the tensilestrength of the cast product from the value of sound velocity andhardness.

FIG. 20 is a block diagram showing an apparatus for implementing thisindirect method, namely, an apparatus for ultrasonic measurement thatmeasures the sound velocity on a cast specimen by ultrasonic wave andwhich computes automatically the tensile strength of the specimen fromthe measured value of sound velocity and the value of hardness asmeasured in a separate step. In FIG. 20, the constituent elements thatare the same as those which are shown in FIG. 16 are identified by likenumerals.

In the drawing, numeral 53 refers to a classification program, 54 is atensile strength computing program, and 55 is a main program, all ofthese programs being new.

These programs are stored in ROM 5 and executed by MPU 9 to perform thefunctions they are assigned respectively.

The operation of the apparatus shown in FIG. 20 is described belowwithout going into details of the part of the operation that has alreadybeen explained in connection with the case shown in FIG. 16. First, thesound velocity on the specimen 1a is measured and stored in area V inRAM 6. Then, the percent spheroidicity of graphite is computed from thestored value of sound velocity in area V in accordance with theempirical V-S conversion formula, and then stored in area S in RAM 6.Stated specifically, this V-S conversion formula is a regression line asis constructed by plotting the results of measurement on a plurality ofcastings in relevant positions on a coordinate system, the horizontalaxis of which may typically represent the sound velocity (V) asdetermined by ultrasonic measurement while the vertical axis representsthe percent spheroidicity of graphite (S) as determined by direct meansof measurement in accordance with the JIS (see 53a in FIG. 17).

When the percent spheroidicity of graphite (S) is determined, theclassification program 53 is activated by the main program 55. Then, thestate of castings structure is classified by the classification program53 in accordance with the value of the percent spheroidicity of graphite(S), and a value indicating the specific type, such as gray cast iron(FC), CV graphite cast iron (FCV), or spheroidal graphite cast iron(FCD), is written into area (F). For the sake of reference, theclassification according to the JIS specifications is shown in FIG. 18.

In the next step, the Brinell hardness of the specimen 1a as measuredwith a separate hardness tester is entered via the keyboard 7 and storedin area HB. Then, the tensile strength computing program 54 is activatedby the main program 55. In accordance with the formula for conversionfrom the product of sound velocity and hardness to tensile strength, theprogram 54 computes the tensile strength from the product of soundvelocity (V) and Brinell hardness (HB) that have been measured on thespecimen 1a. The computed tensile strength is stored in area σB' in RAM6.

It should be noted here that the above-mentioned formula for conversionto tensile strength consists of three expressions that are selectivelyused depending upon the state of castings structure: conversionexpression 54a for FCD, conversion expression 54b for FCV, andconversion expression 54c for FC. Stated specifically, these expressionsare regression lines as constructed by plotting the results of directmeasurement on a plurality of castings in relevant positions on acoordinate system, the horizontal axis of which represents the productof sound velocity and hardness (V×HB) while the vertical axis representsthe tensile strength (σB) (see 54a, 54b, and 54c in FIG. 19).

The thusly determined tensile strength (σB') and the like are displayedon CRT 8 by the main program 55 as the result of measurement.

In the case of spheroidal graphite cast iron and CV graphite cast iron,it is also necessary to know their percent elongation as acharacteristic value for verifying that they are made of the material tospecifications.

The percent elongation of castings has heretofore been measured by amethod that depends on a tensile test as conducted using test pieceshaving a prescribed specification geometry.

However, no convenient and indirect substitute method has ever beendeveloped. As already mentioned, the material species of cast iron canbe specified by the materials characteristic values that are attained bymaterials tests including a tensile test and the like; among them, thepercent spheroidicity of graphite and the tensile strength have been thesubject of reviews on proposed alternatives that rely upon the techniqueof measuring the sound velocity. However, sound velocity measurementusing an apparatus for ultrasonic measurement involves variations in theresult of measurement due to the apparatus such as those in thecharacteristics of the ultrasonic probe, the ultrasonic flaw detectorand D/A conversion. Further, one cannot neglect the variations in theresult of measurement due to the inspector such as those in themeasurement of thickness of the specimen and in adjustments like thesetting of the gate to the ultrasonic flaw detector.

Under these circumstances, the empirical formula on the percentspheroidicity of graphite that has been attained by a certain apparatusand inspector for ultrasonic measurement (see 53a in FIG. 14) does notnecessarily agree with the empirical formula that has been attained byanother apparatus and inspector for ultrasonic measurement (see 53b inFIG. 15). The sound velocity that should correspond to a cast producthaving 70% spheroidicity of graphite is 5.56 km/s in one case but it is5.62 km/s in the other case, and the two values differ considerably.What is more, such differences occur frequently. Therefore, in spite ofthe nondestructive and convenient nature of the measurement, the resultis not reliable and this causes problems.

Next, the specific problems as regards the measurement of the percentspheroidicity of graphite will be further discussed. In the conventionalmethod and apparatus for ultrasonic measurement, an approximate value ofpercent spheroidicity of graphite is computed from the sound velocity inaccordance with an available empirical formula. By means of thisindirect technique, the state of castings structure is analyzed in anondestructive manner.

However, the relationship between the sound velocity and the percentspheroidicity of graphite is such that one does not correlate well tothe other (see FIG. 17). Hence, an approximate value of the percentspheroidicity of graphite that has been attained by the empiricalformula at issue or the result of analysis on the state of castingsstructure contains such large errors that they are by no means suitablefor practical use as substitutes for the true percent spheroidicity ofgraphite.

Under the circumstances, inspections such as nondestructive delivery oracceptance inspection of cast products and the like that have damagehave only low reliability in the results or inspection and, even ifcertain troubles occur in the production process, one may often overlookthe adverse effects of such troubles by failing to detect them.

Similar problems occur in connection with the measurement of tensilestrength on castings. A plurality of formulae exist for conversion totensile strength (see FIG. 19) which are derived on the basis of theresults of measurement on the typical states of casting structures thatbelong to the respective types. Since no general-purpose expression,relation, or the like that unifies them has yet been established, theseformulae are selectively used in accordance with the specific type ofcasting. Under the circumstances, a cast product of an intermediatestate that is not typical is dealt with by different conversion formulaedepending upon the type in which the cast product is classified, andthis causes great variations in the computed result of measurement;hence, the conversion formulae under consideration are by no meanssuitable for practical use as means of warranting the product and thelike.

There are also problems in connection with the measurement of percentelongation on castings. These are drawbacks including the following: Inthe state of the art, the only method that can be adopted is byconducting a tensile test and, since this involves a destructivemeasurement, not all products in the production lot can be inspected;since the geometry of test pieces is prescribed by specifications,several days of time and cost are taken in preparation for themeasurement; and, since a dedicated tensile test apparatus is necessary,no inspectors other than testing organizations and the like which havesuitable apparatus are able to conduct the measurement unless they askfor help by an outsider.

An object, therefore, of the present invention is to solve theseproblems of the prior art by realizing a method and apparatus forultrasonic measurement on castings by which the values of state analysisand characteristic values (e.g. the percent spheroidicity of graphite,state classification, tensile strength, and percent elongation) of castspecimens can be measured or computed with high probability in anondestructive and convenient manner.

DISCLOSURE OF INVENTION

This object of the present invention can be attained by a method ofultrasonic measurement on castings, a first aspect of which is that thesound velocity in a east specimen is measured and a physicalcharacteristic value of the specimen that has a physical correlationwith the sound velocity is determined. According to the method, thesound velocity ratio between the sound velocity in the specimen and thesound velocity in a given metal that corresponds to the specimen(hereafter, the "sound velocity ratio") is attained, and this soundvelocity ratio is converted to the physical quantity of interestaccording to an empirical formula associated with the sound velocityratio or a means of conversion based on the result of measurement,thereby determining the physical characteristic value of the specimen.

The above-mentioned object of the present invention can also be attainedaccording to the invention by an apparatus for ultrasonic measurement oncastings, a first aspect of which measures the sound velocity in a castspecimen and measures a physical characteristic value of the specimenthat has a physical correlation with the sound velocity. Moreparticularly, the apparatus employs an empirical formula by which afirst physical quantity is processed to determine a second physicalquantity that is equivalent to the physical characteristic value or ameans of conversion by which the first physical quantity is converted tothe second quantity which is equivalent to the physical characteristicvalue. A reference sound velocity generating means generates a referencesound velocity by ultrasonic measurement on a steel product.Additionally, a characteristic value generating means determines thephysical quantity by the empirical formula or means of conversion, andgenerates the thus-determined physical quantity as the physicalcharacteristic value, the sound velocity ratio between the soundvelocity in the specimen as attained by ultrasonic measurement on thespecimen and the reference sound velocity being considered an equivalentof the first physical quantity.

Further, the invention defines the quantity as the sound velocity ratiobetween the sound velocity in a certain cast product (specimen) and thesound velocity in the steel product, the two velocities being attainedby measurement with the same apparatus ultrasonic measurement, and thesecond physical quantity as the physical characteristic value that ismeasured on the certain cast product and which is measured directly witha measuring apparatus other than the ultrasonic measurement. Theempirical formula or means of conversion possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between the first physical quantity and thesecond physical quantity which have been measured on a plurality ofsamples of the certain cast product.

In the first aspects of the method and apparatus for ultrasonicmeasurement according to this invention which relates to the measurementto a physical characteristic of castings, the empirical formula and thelike are specified on the basis of the relationship between acharacteristic value of a cast product with respect to the soundvelocity ratio between a steel product and the cast product. Sincevariations in the value of measurement which depend on the apparatus orinspector are likely (more specifically, even the sound velocities asmeasured on a cast product and a steel product by means of the sameapparatus or the like have variations of the same tendency), if theratio between the measured values is taken, the corresponding variationswill cancel each other. Hence, the sound velocity ratio between a steelproduct and a cast product is hardly affected by the influences due tovariations in the apparatus and the like.

Consequently, the empirical formula and the like that are based on thecorrelation between the sound velocity ratio and the characteristicvalue have a wide range of applications and are even effective for otherapparatus or the like that are different from that which has been usedin determining the empirical formula and the like.

Further, the method and apparatus of the present invention forultrasonic measurement of a physical characteristic of castings have theadvantage that when measuring or computing a characteristic value of acast specimen, the sound velocity in a steel product is measuredseparately, or a previously measured value of sound velocity for thesteel product is entered separately, as input data and, on the basis ofthe measured sound velocity in the specimen, the sound velocity ratiobetween the specimen and the steel product is computed. In this case,too, the sound velocity ratio is substantially free from variationssince it is determined by the same apparatus and the like.

Stated more specifically, the empirical formula and the like, which arebased on the relationship between a characteristic value as determinedby a direct method for the measurement of the characteristic value andthe sound velocity ratio, are free from variations and have a wide rangeof applications in that they can be used with any type of apparatus forultrasonic measurement. Then, once the empirical formula and the likeare attained, measurements that involve destruction are not necessary.Further, when measuring a physical characteristic of a cast product asan actual product, the sound velocity in the cast product is normalizedby the sound velocity in the steel product to yield the sound velocityratio and, in accordance with the empirical formula of interest, aphysical characteristic value of the cast product is computed from thesound velocity ratio. In this way, the effect of variations due to theapparatus and the inspector can be eliminated.

Therefore, the physical characteristic value is computed from thevariation-free sound velocity ratio in accordance with thegeneral-purpose formula. As a result, the effect due to similarities ordissimilarities in the apparatus for ultrasonic measurement or theinspector is reduced to the extent that the physical characteristicvalue as associated with the cast specimen can be ultrasonicallymeasured or computed with high probability in a nondestructive andconvenient manner.

The above-mentioned object of the present invention can also be attainedby the method of ultrasonic measurement, a second aspect of whichcomprises a method of measuring the sound velocity in a cast specimenand analyzing the state of casting structure of the specimen that has aphysical correlation with the sound velocity, characterized in that thepercent carbon content of the specimen and the sound velocity in thespecimen are attained. Then, in accordance with an empirical formula ora means of conversion based on the result of measurement, by which ananalytical value equivalent to the state of casting structure isattained from the percent carbon content and sound velocity in a certaincast product, the analytical value corresponding to the percent carboncontent and sound velocity in the specimen is attained, whereby thestate of casting structure in the specimen is analyzed in terms of theanalytical value.

The above-mentioned object of the present invention can also be attainedby the apparatus for ultrasonic measurement, a second aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and analyzes the state of castingstructure in the specimen, characterized in that the apparatus employsan empirical formula by which a first physical quantity and a secondphysical quantity are processed to determine a third physical quantitythat is equivalent to the state of casting structure, or a means ofconversion by which a first physical quantity and a second physicalquantity as two elements are converted to a third physical quantity thatis equivalent to the state of casting structure; and a state evaluatingmeans which determines the third physical quantity by the empiricalformula or the means of conversion, provided that the sound velocity inthe specimen as attained by ultrasonic measurement on the specimen isdealt with as or considered to be an equivalent of the first physicalquantity, and that the percent carbon content is dealt with as anequivalent of the second physical quantity, the means evaluating thestate of casting structure in accordance with the thusly determinedthird physical quantity.

Further, the first physical quantity is the sound velocity in a certaincast product according to the invention, the second physical quantity isthe percent carbon content of the certain cast product, the thirdphysical quantity is the state of casting structure that is measured onthe certain cast product and which is measured directly with a measuringapparatus other than the ultrasonic measurement apparatus, and theempirical formula or means of conversion possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between the first physical quantity, thesecond physical quantity, and the third physical quantity which havebeen measured on a plurality of samples of the certain cast product.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a third aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and analyzes the state of castingstructure in the specimen, characterized in that the apparatus employsan empirical formula by which a first physical quantity and a secondphysical quantity are processed to determine a third physical quantitythat is equivalent to the state of casting structure, or a means ofconversion by which a first physical quantity and a second physicalquantity are converted to a third physical quantity that is equivalentto the state of casting structure; a reference sound velocity generatingmeans generates the sound velocity, as attained by ultrasonicmeasurement on a steel product, as a reference sound velocity; and astate evaluating means determines the third physical quantity by theempirical formula or the means of conversion, provided that the soundvelocity ratio, measured between the sound velocity in the specimen asattained by ultrasonic measurement on the specimen and the referencesound velocity, is dealt with as the first physical quantity, andprovided that the percent carbon content is dealt with as an equivalentof the second physical quantity, the means evaluating the state ofcasting structure in accordance with the thusly determined thirdphysical quantity.

The third aspect of the apparatus is further characterized in that thefirst physical quantity is the sound velocity ratio between a certaincast product and the steel product as attained by measurement with thesame apparatus for ultrasonic measurement, in that the second physicalquantity is the percent carbon content of the certain cast product, inthat the third physical quantity is the state of casting structure thatis measured on the certain cast product and which is measured directlywith a measuring apparatus other than the one for ultrasonicmeasurement, and in that the empirical formula or means of conversionpossesses either a characteristic function, a table, or a processingprocedure that represents the correlation between the first physicalquantity, the second physical quantity, and the third physical quantity,which have been measured on a plurality of samples of the certain castproduct.

Thus, the second aspect of the method of ultrasonic measurementaccording to the present invention, as well as the second and thirdaspects of the apparatus for ultrasonic measurement, analyze the stateof casting structure with a view to performing classification or thelike, particularly on castings, by ultrasonic measurement, and theanalysis is performed on the basis of both the present carbon contentand the sound velocity or sound velocity ratio (which are hereunderabbreviated as the "sound velocity or the like"). To this end, the stateof casting structure as it relates to the percent carbon content and thesound velocity or the like is measured by a direct means or the like,and the formula or means of conversion that represent the relationshipbetween those factors is specified experimentally. By thusly performingstate classification based not only on the sound velocity or the likebut also on the percent carbon content, it is now possible to clearlyclassify the state of casting structure which has heretofore beendifficult to classify, and in particular, the state of casting structureas regards the morphology of graphite or the like.

Then, in accordance with the list or the like which has been determinedby the direct method of measurement, the state of casting structure ofthe specimen is evaluated on the basis of the sound velocity or the likethat has been determined by ultrasonic measurement and its percentcarbon content. Thus, a close analysis is performed on the basis of notonly the sound velocity or the like but also the percent carbon contentand, therefore, in spite of its indirect nature, the analysis permitsthe state of casting structure to be estimated more closely and morecorrectly than has heretofore been possible.

Consequently, the state of casting structure that is associated with thecast specimen can be measured or analyzed with high probability byultrasonic measurement in a nondestructive and convenient manner.

The above-stated object of the present invention can also be attained bythe method of ultrasonic measurement, a third aspect of which comprisesultrasonic measurement in which the sound velocity in a cast specimen ismeasured and the tensile strength of the specimen is determined,characterized in that the percent content and the hardness of thespecimen, as well as the sound velocity in the specimen, are attainedand that, in accordance with an empirical formula or a means ofconversion based on the result of measurement, by which the tensilestrength is attained from the percent carbon content and the hardness ofa certain cast product and the sound velocity in the cast product, thetensile strength of the specimen is determined from the percent carboncontent and the hardness of the specimen and the sound velocity in thespecimen.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a fourth aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and measures the tensile strength ofthe specimen, characterized in that the apparatus employs an empiricalformula by which a first physical quantity, a second physical quantity,and a third physical quantity are processed to determine a fourthphysical quantity that is equivalent to the tensile strength, or a meansof conversion by which a first physical quantity, a second physicalquantity, and a third physical quantity as three elements are convertedto a fourth physical quantity that is equivalent to the tensilestrength; and a tensile strength computing means determines the fourthphysical quantity by the empirical formula or the means of conversion,provided that the sound velocity in the specimen, as attained byultrasonic measurement on the specimen, is dealt with as an equivalentof the first physical quantity, the percent carbon content as anequivalent of the second physical quantity, and the hardness of thespecimen as an equivalent of the third physical quantity, the meansoutputting the thusly determined fourth physical quantity as the valueof the tensile strength.

The fourth aspect is further characterized in that the first physicalquantity is the sound velocity in a certain cast product, in that thesecond physical quantity is the percent carbon content of the certaincast product, in that the third physical quantity is the hardness of thecertain cast product, in that the fourth physical quantity is thetensile strength as measured on the certain cast product by a directmeans of tensile strength measurement other than the apparatus forultrasonic measurement, and in that the empirical formula or the meansof conversion possesses either a characteristic function, a table, or aprocessing procedure that represents the correlation between the firstphysical quantity, the second physical quantity, the third physicalquantity, and the fourth physical quantity which have been measured on aplurality of samples of the certain cast product.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a fifth aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and measures the tensile strength ofthe specimen, characterized in that the apparatus employs an empiricalformula by which a first physical quantity, a second physical quantity,and a third physical quantity are processed to determine a fourthphysical quantity that is equivalent to the tensile strength, or a meansof conversion by which a first physical quantity, a second physicalquantity, and a third physical quantity as three elements are convertedto a fourth physical quantity that is equivalent to the tensilestrength; a reference sound velocity generating means by which the soundvelocity as attained by ultrasonic measurement on a steel product isgenerated as a reference sound velocity; and a tensile strengthcomputing means which determines the fourth physical quantity by theempirical formula or conversion means, provided that the sound velocityratio between the sound velocity in the specimen and the reference soundvelocity is dealt with as an equivalent of the first physical quantity,the percent carbon content as an equivalent of the second physicalquantity, and the hardness of the specimen as an equivalent of the thirdphysical quantity, the means outputting the thusly determined fourthphysical quantity as the value of the tensile strength.

The fifth aspect is further characterized in that the first physicalquantity is the sound velocity ratio between the sound velocity in acertain cast product and the sound velocity in the steel product, thetwo velocities being attained by measurement with the same apparatus forultrasonic measurement; in that the second physical quantity is thepercent carbon content of the certain cast product; in that the thirdphysical quantity is the hardness of the certain cast product; in thatthe fourth physical quantity is the tensile strength as measured on thecertain cast product by a direct means of tensile strength measurementother than the apparatus for ultrasonic measurement; and in that theempirical formula or conversion means possesses either a characteristicfunction, a table, or a processing procedure that represents thecorrelation between the first physical quantity, the second physicalquantity, the third physical quantity, and the fourth physical quantitywhich have been measured on a plurality of samples of the certain castproduct.

Thus, the third aspect of the method of ultrasonic measurement accordingto the present invention, as well as the fourth and fifth aspects of theapparatus for ultrasonic measurement, computes the tensile strength,particularly on castings, by ultrasonic measurement, and the computationof tensile strength is performed on the basis of the percent carboncontent, the hardness, and the sound velocity or sound velocity ratio.To perform this computation or the like, the tensile strength of thecast product of interest as it relates to the percent carbon content,the hardness, and the sound velocity or the like is measured by a directmeans or the like, and the formula or means of conversion thatrepresents the relationship between those factors is specifiedpreliminarily on an experimental basis.

By thusly establishing correlation to the tensile strength based notonly on the sound velocity and hardness but also on the percent carboncontent, the overlap between data of measurement of tensile strengthwill be limited not only for castings in a typical state but also forcastings in an intermediate state and, as a result, the data to bemeasured can be clearly correlated to the data to be computed. Inaccordance with the empirical formula or the like under consideration,the tensile strength of the cast specimen is computed from the percentcarbon content and the hardness of the specimen, as well as the soundvelocity or the like in the specimen. By so doing, the analysis, eventhough an indirect method, permits the tensile strength of the castproduct to be estimated in a closer and more correct way than hasheretofore been possible.

Consequently, the tensile strength of the cast specimen, which is one ofits characteristic values, can be measured or computed with highprobability by means of ultrasonic measurement in a nondestructive andconvenient manner.

The above-stated object of the present invention can also be attained bythe method of ultrasonic measurement, a fourth aspect of which comprisessteps in which the sound velocity in a cast specimen is measured and thepercent elongation of the specimen is determined, characterized in thatthe percent carbon content and the hardness of the specimen, as well asthe sound velocity in the specimen, are attained and that, in accordancewith an empirical formula or a means of conversion based on the resultof measurement, by which the percent elongation is attained from thepercent carbon content and the hardness of a certain cast product andthe sound velocity in the product, the percent elongation of thespecimen is determined from the percent carbon content and the hardnessof the specimen and the sound velocity in the specimen.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a sixth aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and measures the percent elongationof the specimen, characterized in that the apparatus employs anempirical formula by which a first physical quantity, a second physicalquantity, and a third physical quantity are processed to determine afourth physical quantity that is equivalent to the percent elongation,or a means of conversion by which a first physical quantity, a secondphysical quantity, and a third physical quantity as three elements areconverted to a fourth physical quantity that is equivalent to thepercent elongation; and a percent elongation computing means whichdetermines the fourth physical quantity by the empirical formula orconversion means, provided that the sound velocity in the specimen asattained by ultrasonic measurement on the specimen is dealt with as anequivalent of the first physical quantity, the percent carbon content asan equivalent of the second physical quantity, and the hardness of thespecimen as an equivalent of the third physical quantity, the meansoutputting the thusly determined fourth physical quantity as the valueof the percent elongation.

The sixth aspect is further characterized in that the first physicalquantity is the sound velocity in a certain cast product; in that thesecond physical quantity is the percent carbon content of the certaincast product; in that the third physical quantity is the hardness of thecertain cast product; in that the fourth physical quantity is thepercent elongation as measured on the certain cast product by a directmeans of percent elongation measurement other than the apparatus forultrasonic measurement; and in that the empirical formula or conversionmeans possesses either a characteristic function, a table, or aprocessing procedure that represents the correlation between the firstphysical quantity, the second physical quantity, the third physicalquantity, and the fourth physical quantity which have been measured on aplurality of samples of the certain cast product.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a seventh aspect of whichcomprises structure which measures the sound velocity in a cast specimenwith a known percent carbon content and measures the percent elongationof the specimen, characterized in that the apparatus employs anempirical formula by which a first physical quantity, a second physicalquantity, and a third physical quantity are processed to determine afourth physical quantity that is equivalent to the percent elongation,or a means of conversion by which a first physical quantity, a secondphysical quantity, and a third physical quantity as three elements areconverted to a fourth physical quantity that is equivalent to thepercent elongation; a reference sound velocity generating means by whichthe sound velocity as attained by ultrasonic measurement on a steelproduct is generated as a reference sound velocity; and a percentelongation computing means which determines the fourth physical quantityby the empirical formula or conversion means, provided that the soundvelocity ratio between the sound velocity in the specimen as attained byultrasonic measurement on the specimen and the reference sound velocityis dealt with as an equivalent of the first physical quantity, thepercent carbon content as an equivalent of the second physical quantity,and the hardness of the specimen as an equivalent of the third physicalquantity, the means outputting the thusly determined fourth physicalquantity as the value of the percent elongation.

The seventh aspect is further characterized in that the first physicalquantity is the sound velocity ratio between the sound velocity in acertain cast product and the sound velocity in the steel product, thetwo velocities being attained by measurement with the same apparatus forultrasonic measurement; in that the second physical quantity is thepercent carbon content of the certain cast product; in that the thirdphysical quantity is the hardness of the certain cast product; in thatthe fourth physical quantity is the percent elongation as measured onthe certain cast product by a direct means of percent elongationmeasurement other than the apparatus for ultrasonic measurement; and inthat the empirical formula or conversion means possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between the first physical quantity, thesecond physical quantity, the third physical quantity, and the fourthphysical quantity which have been measured on a plurality of samples ofthe certain cast product.

The above-stated object of the present invention can also be attained bythe method of ultrasonic measurement, a fifth aspect of which comprisessteps in which the sound velocity in a cast specimen is measured and thepercent elongation of the specimen is determined, characterized in thatthe specimen is a copper-containing cast iron, that the percent coppercontent, the percent carbon content, and the hardness of the specimen,as well as the sound velocity in the specimen are attained and that, inaccordance with a function, a table, or some other means of conversionfor attaining the percent elongation from the percent copper content,and the hardness of a certain cast product and the sound velocity in theproduct, the percent elongation of the specimen is determined from thepercent copper content, the percent carbon content, and the hardness ofthe specimen and the sound velocity in the specimen.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, an eighth aspect of whichcomprises structure which measures the sound velocity in a specimenformed of a copper-containing cast iron with known percent copper andcarbon contents, and measures the percent elongation of the specimen,characterized in that the apparatus employs an empirical formula bywhich a first physical quantity, a second physical quantity, a thirdphysical quantity, and a fourth physical quantity are processed todetermine a fifth physical quantity that is equivalent to the percentelongation, or a means of conversion by which a first physical quantity,a second physical quantity, a third physical quantity, and a fourthphysical quantity as four elements are converted to a fifth physicalquantity that is equivalent to the percent elongation; and a percentelongation computing means which determines the fifth physical quantityby the empirical formula or conversion means, provided that the soundvelocity in the specimen as attained by ultrasonic measurement on thespecimen is dealt with as an equivalent of the first physical quantity,the percent carbon content as an equivalent of the second physicalquantity, the hardness of the specimen as an equivalent of the thirdphysical quantity, and the percent copper content as an equivalent ofthe fourth physical quantity, the means outputting the thusly determinedfifth physical quantity as the value of the percent elongation.

The fifth aspect is further characterized in that the first physicalquantity is the sound velocity in a certain copper-containing cast iron;in that the second physical quantity is the percent carbon content ofthe certain copper-containing cast iron; in that the third physicalquantity is the hardness of the certain copper-containing cast iron; inthat the fourth physical quantity is the percent copper content of thecertain copper-containing cast iron; in that the fifth physical quantityis the percent elongation as measured on the certain copper-containingcast iron by a direct means of percent elongation measurement other thanthe apparatus for ultrasonic measurement; and in that the empiricalformula or conversion means possesses either a characteristic function,a table, or a processing procedure that represents the correlationbetween the first physical quantity, the second physical quantity, thethird physical quantity, the fourth physical quantity, and the fifthphysical quantity which have been measured on a plurality of samples ofthe certain copper-containing cast iron.

The above-stated object of the present invention can also be attained bythe apparatus for ultrasonic measurement, a ninth aspect of whichcomprises an apparatus for ultrasonic measurement which measures thesound velocity in a specimen formed of a copper-containing cast ironwith known percent copper and carbon contents and measures the percentelongation of the specimen, characterized in that the apparatus employsan empirical formula by which a first physical quantity, a secondphysical quantity, a third physical quantity, and a fourth physicalquantity are processed to determine a fifth physical quantity that isequivalent to the percent elongation, or a means of conversion by whicha first physical quantity, a second physical quantity, a third physicalquantity, and a fourth physical quantity as four elements are convertedto a fifth physical quantity that is equivalent to the percentelongation; a reference sound velocity generating means by which thesound velocity as attained by ultrasonic measurement on a steel productis generated as a reference sound velocity; and a percent elongationcomputing means which determines the fifth physical quantity by theempirical formula or conversion means, provided that the sound velocityratio between the sound velocity in the specimen as attained byultrasonic measurement on the specimen and the reference sound velocityis dealt with as an equivalent of the first physical quantity, thepercent carbon content as an equivalent of the second physical quantity,the hardness of the specimen as an equivalent of the third physicalquantity, and the percent copper content as an equivalent of the fourthphysical quantity, the means outputting the thusly determined fifthphysical quantity as the value of the percent elongation.

The ninth aspect is further characterized in that the first physicalquantity is the sound velocity ratio between the sound velocity in acertain copper-containing cast iron and the sound velocity in the steelproduct, the two velocities being attained by measurement with the sameapparatus for ultrasonic measurement; in that the second physicalquantity is the percent carbon content of the certain copper-containingcast iron; in that the third physical quantity is the hardness of thecertain copper-containing cast iron; in that the fourth physicalquantity is the percent copper content of the certain copper-containingcast iron; in that the fifth physical quantity is the percent elongationas measured on the certain copper-containing cast iron by a direct meansof percent elongation measurement other than the apparatus forultrasonic measurement; and in that the empirical formula or conversionmeans possesses either a characteristic function, a table, or aprocessing procedure that represents the correlation between the firstphysical quantity, the second physical quantity, the third physicalquantity, the fourth physical quantity, and the fifth physical quantitywhich have been measured on a plurality of samples of the certaincopper-containing cast iron.

Thus, the fourth and fifth aspects of the method of ultrasonicmeasurement according to the present invention, as well as the sixth,seventh, eighth, and ninth aspects of the apparatus for ultrasonicmeasurement, compute the percent elongation, particularly on castings,by ultrasonic measurement, and the computation of the percent elongationof castings is performed on the basis of the percent carbon content, thehardness, and the sound velocity or sound velocity ratio (or acombination of these with the percent copper content). To perform thiscomputation or the like, the percent elongation of the cast product ofinterest as it relates to the percent carbon content, the hardness, andthe sound velocity or the like (or a combination of these with thepercent copper content) is measured by a direct means or the like, andthe formula or means of conversion that represents the relationshipbetween these factors is specified preliminarily on an experimentalbasis.

By thusly establishing correlation to the percent elongation based notonly on the sound velocity and hardness but also on the percent carboncontent (or a combination of these with the percent copper content), thedata to be measured can be clearly correlated to the data to be computedalthough these data have not heretofore been correlated to each other.In accordance with the empirical formula or the like underconsideration, the percent elongation of the cast specimen is computedfrom the percent carbon content and the hardness of the specimen, andthe sound velocity or the like in the specimen (or a combination ofthese with the percent copper content) and, by so doing, the percentelongation of the cast product can be estimated. In other words, thepercent elongation of castings can be measured indirectly although thishas heretofore been impossible.

Consequently, the percent elongation of the cast specimen, which is oneof its characteristic values, can be measured or computed with highprobability by means of ultrasonic measurement in a nondestructive andconvenient manner.

If, in addition to the percent carbon content, the percent coppercontent is also included as a parameter, there is achieved a particularadvantage in that, even in the case where the cast product to beanalyzed is a copper-containing cast iron, its percent elongation can bemeasured in a nondestructive and convenient manner.

It should be noted here that as regards all of the above-describedaspects of the method and apparatus for ultrasonic measurement, thepercent carbon content may be replaced by the carbon equivalent.

It should also be noted that while the above-described empirical formulaor means of conversion possesses a characteristic function, a table, ora processing procedure, the concept of this characteristic function ortable embraces various items such as diagrams, graphic charts, lists,approximations, and so-called sequences, maps, tables, etc. that arerelated to computer programs; further, the concept of the processingprocedure embraces means of conversion such as a computing procedure, amathematical operation, a process, address tables, etc. that use ormodify such a processing procedure.

The percent carbon content (or its combination with the percent coppercontent) which is held to be necessary for the present invention isfamiliar to the manufacturer who presets the proportions of componentsin the casting material, but usually the customer who accepts the castproduct is also in the position to be knowledgeable of that factor asone of the conditions for placement of an order; therefore, aside fromthe special case where a cast product of unknown origin has to beanalyzed for research and experimental purposes, the factor underconsideration will be no impediment to practical implementation of thepresent invention. Measurement of the hardness of the specimen alsocauses no inconvenience since this can be performed with a hardnessmeter that is simple to operate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a first example of the apparatus forultrasonic measurement which features the constitution of the presentinvention, and which computes automatically the percent spheroidicity ofgraphite as one of the physical characteristic values of a cast product;

FIG. 2 is a block diagram showing a second example of the apparatus forultrasonic measurement which features the constitution of the presentinvention, and which analyzes automatically the state of castingstructure;

FIG. 3, relating to the second example, shows an example of theassociated conversion map;

FIG. 4 is a block diagram showing a third example of the apparatus forultrasonic measurement which features the constitution of the presentinvention, and which measures or computes automatically the tensilestrength of a cast product;

FIG. 5, relating to the third example, shows in graphic form thecorrespondence between the computed index value α' of the cast product(horizontal axis) and the measured hardness coefficient m (verticalaxis);

FIG. 6, relating to the third example, shows in graphic form thecorrespondence between the computed tensile strength σB' (horizontalaxis) and the measured tensile strength σB (vertical axis);

FIG. 7 is a block diagram showing a fourth example of the apparatus forultrasonic measurement which features the constitution of the presentinvention, and which measures or computes automatically the percentelongation of a cast product;

FIG. 8, relating to the fourth example, shows in graphic form thecorrespondence between the computed index value α' (horizontal axis) andthe product of tensile strength σB' and percent elongation ε (σB'×ε)(vertical axis);

FIG. 9, relating to the fourth example, shows in graphic form thecorrespondence between the computed percent elongation ε' (horizontalaxis) and the measured percent elongation ε (vertical axis);

FIG. 10 is a block diagram showing a fifth example of the apparatus forultrasonic measurement which features the constitution of the presentinvention, and which measures or computes automatically the percentelongation of a copper-containing cast iron;

FIG. 11, relating to the fifth example, shows in graphic form thecorrespondence between the computed value (ε'/(2× Cu)) (horizontal axis)and the measured percent elongation ε (vertical axis);

FIG. 12, relating to the fifth example, shows in graphic form thecorrespondence between the computed percent elongation ε" (horizontalaxis) and the measured percent elongation ε (vertical axis);

FIG. 13 is a diagrammatic presentation of examples of the morphology ofgraphite in castings;

FIG. 14 is an example of the relationship between the sound velocity incastings and the percent spheroidicity of graphite;

FIG. 15 is another example of the relationship between the soundvelocity in castings and the percent spheroidicity of graphite;

FIG. 16 is a block diagram of a conventional apparatus for measuring thepercent spheroidicity of graphite;

FIG. 17 is yet another example of the relationship between the soundvelocity in castings and the percent spheroidicity of graphite;

FIG. 18 is a chart illustrating the morphology and classification ofgraphite types in castings;

FIG. 19 shows in graphic form the correspondence between (soundvelocity×hardness) and tensile strength; and

FIG. 20 is a block diagram of a conventional apparatus for measuring thetensile strength of castings.

BEST MODE FOR CARRYING OUT THE INVENTION

A first example of the present invention is described below in detailwith reference to the drawings. FIG. 1 is a block diagram showing anapparatus for implementing the method of the present invention forultrasonic measurement of a physical characteristic of castings, namely,an apparatus for ultrasonic measurement that measures the sound velocityin a cast specimen by ultrasonic energy, and which computesautomatically the percent spheroidicity of graphite in the specimen.

In the diagram, numeral 1 designates an ultrasonic probe, 2 anultrasonic flaw detector, 3 a D/A converter circuit, 4 a bus line, 5 aROM, 6 a RAM, 7 a keyboard (KBD), 8 a CRT, and 9 a microprocessor (MPU).Details of interface circuits and the like that are connected betweenthese components are omitted from FIG. 1.

Further referring to FIG. 1, numeral 51 designates a program formeasuring the sound velocity, 511 is a program for setting the soundvelocity in steel, 512 is a program for normalizing the sound velocity,523 is a program for computing the percent spheroidicity, 530 is a(V/Vm)-S conversion formula, and 550 is a main program; these programsare stored in ROM 5 and executed by MPU 9 to perform the functionsrespectively assigned to them.

It should be noted that ultrasonic probe 1 through microprocessor 9 andsound velocity measuring program 51 have the same configurations as inthe prior art and, hence, they are identified by like numerals and theirexplanation is not repeated.

The main program 550 is an overall measurement managing program and hastwo selectable modes, namely a first mode for setting the sound velocityin steel and a second mode for measuring the percent spheroidicity ofgraphite in castings. In response to either mode, the main programactivates other programs and controls the order in which they areexecuted.

The sound-velocity-in-steel program 511 is a sub-program for setting thesound velocity in steel, which serves as a reference value. The value ofsound velocity that is measured with the sound velocity measuringprogram 51 and which is stored in area V is transferred by the program511 into area Vm in RAM 6, where it is set as the sound velocity insteel.

The sound velocity normalizing program 512 is a sub-program forcomputing the sound velocity ratio. The value of sound velocity that ismeasured with the sound velocity measuring program 51 and which isstored in area V is divided by the sound velocity in steel which isstored as the reference value in area Vm, and the thusly computed soundvelocity ratio is placed by the program 512 in area (V/Vm) in RAM 6.

The percent spheroidicity computing program 523 is a sub-program forcomputing the percent spheroidicity of graphite; it performs aconversion process in accordance with the (V/Vm)-S conversion formula530 and computes the percent spheroidicity of graphite from the value ofthe sound velocity ratio in area (V/Vm). The thusly computed percentspheroidicity of graphite is stored in area S in RAM 6.

The (V/Vm)-S conversion formula 530 is an experimentally predeterminedconversion formula and represents the relationship that the percentspheroidicity of graphite (s) has with respect to the sound velocityratio between the steel and cast product ((V/Vm)).

Stated more specifically, a number of cast products are first providedthat resemble each other in shape as closely as possible, and at leastone steel product is also provided. Then, the sound velocity in thesecast and steel products is measured with an apparatus for ultrasonicmeasurement, and the sound velocity ratio computed between the cast andsteel products. Further, the percent spheroidicity of graphite in eachcast product is measured by a direct method in accordance with or asadapted from JIS specifications. It should be noted that, in order toensure agreement in the tendency of variations, the series ofdestructive measurements are desirably performed with the same apparatusfor ultrasonic measurement by the same inspector if possible.

Since this direct measurement is time-consuming, it is recommended thatanother series of measurements be performed in parallel on another groupof cast products and on at least one steel product by another set ofapparatus for ultrasonic measurement and by another inspector so as toyield a large number of measurement results.

The thusly obtained large number of measurement results are plotted inrelevant positions on a coordinate system, the horizontal axis of whichmay typically represent the sound velocity ratio ((V/Vm)) while thevertical axis represents the percent spheroidicity of graphite (S) asmeasured by direct means.

In this case, the sound velocity ratio as the normalized sound velocityis taken on the horizontal axis and, since it is free from any effectsdue to the apparatus and inspector, the results of the above-mentionedseries of measurement and those of another series of measurement may bepresented on one graphic chart without causing any inconvenience. Hence,the distribution diagram having its statistical reliability improved asa result of plotting the results of a large number of measurements, canbe expressed by a regression line or approximated by a kinked line toyield the (V/Vm)-S conversion formula 530. For the same reason, theconversion formula 530 is in no way limited to a particular apparatusand, once it is computed, is applicable as such to any other types ofapparatus for ultrasonic measurement.

With this configuration, the process of measuring the percentspheroidicity of graphite in castings starts with measuring the soundvelocity in a steel product in mode 1 (the mode for setting the soundvelocity in steel), followed by processing cast products successively inmode 2 (the mode for measuring the percent spheroidicity of graphite incastings).

Stated in detail, a steel product that is as similar as possible inshape to the cast products is provided as specimen 1a. Then, the mainprogram 550 is instructed to perform processing in mode 1. In this mode1, the main program 550 activates the sound velocity measuring program51 and the sound velocity in the steel product is stored in area V.Then, the sound-velocity-in-steel setting program 511 as activated bythe main program 550 sets the resulting sound velocity in the steelproduct in area Vm. In the case where the sound velocity in steel wasalready measured under the same conditions on the previous day or thelike, the sound velocity measurement may be omitted and alternatively apredetermined value of sound velocity in steel that has been entered viakeyboard 7 may be set in area Vm.

Next, one of the cast products is used as specimen 1a. Then, the mainprogram 550 is instructed to perform processing in mode 2. In this mode2, the main program 550 activates the sound velocity measuring program51, and the sound velocity in the cast product being analyzed is storedin area V. Thereafter, the main program 550 activates the sound velocitynormalizing program 512, and the sound velocity ratio as computed fromthe sound velocity (V) in the cast product being analyzed and the soundvelocity (Vm) in steel is set in area (V/Vm).

Subsequently, the percent spheroidicity computing program 523 isactivated, and this program 523 performs a conversion process inaccordance with the (V/Vm)-S conversion formula 530 and computes thepercent spheroidicity of graphite (S) from the value of sound velocityratio in area (V/Vm). The thusly computed percent spheroidicity ofgraphite is stored in area S in RAM 6.

The reliable percent spheroidicity of graphite as computed from thenormalized sound velocity ratio on the basis of the normalized empiricalformula 530 is displayed on CRT 8 by the main program 550 as the resultof measurement.

Thus, an approximate value of the percent spheroidicity of graphite inone cast product can be measured with high reliability in anondestructive and easy manner.

Since the sound velocity in the steel product need be measured onlyonce, each of the remaining cast products may be used successively asspecimen 1a for subsequent measurements of the percent spheroidicity ofgraphite.

It should be mentioned that the percent spheroidicity of graphite isgiven to illustrate one characteristic value in connection with thephysical characteristics of castings, and the operational effect ofnormalization by the sound velocity in steel will hold equally withother physical characteristic values of castings.

A second example of the present invention is described below in detailwith reference to the drawings. FIG. 2 is a block diagram showing anapparatus for implementing the method of the present invention foranalyzing the state of casting structure, namely, an apparatus forultrasonic measurement that measures the sound velocity in a castspecimen by ultrasonic energy and which analyzes automatically the stateof casting structure in the specimen.

To explain the constituent elements that differ from those shown in FIG.1, the percent spheroidicity computing program 523 is replaced by astate evaluating program 523p, and the (V/Vm)-S conversion map 530 isreplaced by a ((V/Vm),C)-S' conversion map 530p; the program is storedin ROM 5 and processed for execution by MPU 9 to perform the function itis assigned.

The main program 550 has both the first mode for setting the soundvelocity in steel and the second mode for analyzing the state of castingstructure. In response to either mode, the main program 550 activatesother programs and controls the order in which they are executed.

The state evaluating program 523p is a sub-program for evaluating thestate of casting structure; it performs a conversion process inaccordance with the ((V/Vm), C)-S' conversion map 530p and evaluates thestate of casting structure on the basis of both the value of soundvelocity ratio in area (V/Vm) and the value of percent carbon content inarea C. The thusly evaluated state of casting structure is stored inarea S' in RAM 6.

The ((V/Vm),C)-S' conversion map 530p is an experimentally predeterminedconversion map and represents the relationship the state of castingstructure (S') has with respect to the sound velocity ratio ((V/Vm))between the steel and cast product, and to the present carbon content ofthe cast product under analysis.

Stated more specifically, a number of cast products are first providedthat resemble each other in shape as closely as possible but whichdiffer in percent carbon content, and at least one steel product is alsoprovided. Then, the sound velocity in these cast and steel products ismeasured with an apparatus for ultrasonic measurement, and the soundvelocity ratio between the cast and steel products is computed. Further,a direct method is used in accordance with or as adapted from JISspecifications to measure the state of casting structure, for instance,to check whether the morphology of graphite grains in each cast productis like flakes, vermicular, or spheroids (FC, FCV, FCD). It should benoted that, in order to ensure agreement in the tendency of variations,the series of destructive measurements are desirably performed with thesame apparatus for ultrasonic measurement by the same inspector ifpossible.

Since this direct measurement is time-consuming, it is recommended thatanother series of measurements be performed in parallel on another groupof cast products and on at least one steel product by another set ofapparatus for ultrasonic measurement and inspector so as to yield alarge number of results of measurement.

The thusly obtained large number of measurement results are plotted in acoordinate system, with the horizontal axis typically plotting the soundvelocity ratio (V/Vm) and the vertical axis plotting the percent carboncontent (C), and the state of casting structure (FC, FCV, FCD) asevaluated by a direct means of measurement is set in a coordinateposition that corresponds to the sound velocity ratio and the percentcarbon content at the time of measurement under consideration.

If, in this case, the sound velocity ratio is plotted on the horizontalline, any effects due to the apparatus and inspector are eliminated, andan even higher probability is assured than in the case where merely thesound velocity is adopted.

It is recommended that the state of casting structure to be set ispreferably freed of variable components by performing statisticalprocessing such as decision making by majority, averaging, localaveraging, or regression analysis on the results of the largest possiblenumber of measurements. The state of casting structure may beexemplified by the hardness coefficient (m) and the above-mentionedmorphological classification of graphite grains (FC, FCV, FCD); ifdesired, the percent spheroidicity of graphite in accordance withspecifications of the JIS (Japanese Industrial Standards) may beadopted.

The adoption of the map which is based on the sound velocity and percentcarbon content enables various regions to be clearly separated althoughthey have been found to overlap partly according to the conventionalclassification, which is based solely on the sound velocity. Further, inaddition, it is possible to classify even the state of casting structurein a region intermediate between two regions FC and FCV (see region FC'in FIG. 3).

With this configuration, the process of measuring the state of castingstructure starts with measuring the sound velocity in a steel product ina mode 1 (the mode for setting the sound velocity in steel), followed byprocessing cast products successively in mode 2 (the mode for measuringthe percent spheroidicity of graphite in castings).

To state in detail, without regard to partial overlap with thealready-described first example, a steel product that is as similar aspossible in shape to the cast products is provided as specimen 1a. Then,the main program 550 is instructed to perform processing in mode 1. Inthis mode 1, the main program 550 activates the sound velocity measuringprogram 51, and the sound velocity in the steel product is stored inarea V. Then, the sound-velocity-in-steel setting program 511 asactivated by the main program 550 sets the resulting sound velocity insteel product in area Vm. In the case where the sound velocity in steelwas already measured under the same conditions on the previous day orthe like, the sound velocity measurement may be omitted, andalternatively a predetermined value of sound velocity in steel that hasbeen entered via keyboard 7 may be set in area Vm.

Next, one of the cast products is used as specimen 1a. Then, the mainprogram 550 is instructed to perform processing in mode 2. In the firststep of this mode 2, the percent carbon content of cast specimen 1a(which is known as one of the data for the casting operation) is enteredvia keyboard 7 and set in area (C). If this data entry is omitted,processing is performed on the assumption that the percent carboncontent is the same as that of the previous specimen. In the subsequentsecond step, the main program 550 activates the sound velocity measuringprogram 51, and the sound velocity in the cast product being analyzed isstored in area V. Thereafter, in the third step, the main program 550activates the sound velocity normalizing program 512, and the soundvelocity ratio as computed from the sound velocity (V) in the castproduct being analyzed and the sound velocity (Vm) in steel is set inarea (V/Vm).

Subsequently, in the fourth step, the state evaluating program 523p isactivated, and this program 523p performs a conversion process inaccordance with the ((V/Vm),C)-S' conversion map 530p and evaluates thestate of casting structure in terms of the value of the position in themap that corresponds to the value of sound velocity ratio in area (V/Vm)and the value of percent carbon content in area (C). The thuslyevaluated state of casting structure is stored in area S in RAM 6.

The reliable state of casting structure, as evaluated by closeclassification with respect to the sound velocity ratio and percentcarbon content on the basis of the conversion map 530p, is displayed onCRT 8 by the main program 550 as the result of measurement. Forinstance, if heats that have been adjusted in components and the likewith a view to producing spheroidal graphite cast iron having hightoughness turn into CV cast iron of lower toughness or flaky cast ironas a result of delay in processing time or the like (see arrows 520f and530g in FIG. 3), this fact and the like can be detected in a positiveand nondestructive manner.

Thus, the state of casting structure can be analyzed on a single castproduct with high reliability in a nondestructive and easy manner.

Since the sound velocity in the steel product need be measured onlyonce, each of the remaining cast products may successively be used asspecimen 1a for subsequent analyses of the state of casting structure onthose products.

A third example of the present invention is described below withreference to the drawings. FIG. 4 is a block diagram of an apparatus forultrasonic measurement that measures the sound velocity in a castspecimen by ultrasonic wave energy, and which computes automatically thetensile strength of that specimen.

The configuration of this apparatus is basically similar to that of thealready-described second example, except that the state evaluatingprogram 523 in the second example is replaced by a new program 540 andassociated elements for computing the tensile strength.

To explain the constituent elements that differ from those shown in FIG.2, the tensile strength computing program 540 is a sub-program forcomputing the tensile strength of castings; it performs a specifiedconversion process to compute the tensile strength of a cast product onthe basis of three values: the value of sound velocity ratio in area(V/Vm), the value of percent carbon content in area C, and the value ofBrinell hardness in area HB. The thusly computed tensile strength of thecast product is stored in area σB' in RAM 6.

The specified conversion process is an experimentally predeterminedcomputing procedure for computing the tensile strength (σB') of a castproduct on the basis of the relationship that its tensile strength (σB)has with respect to the sound velocity ratio (V/Vm) between the steeland cast product, the percent carbon content (C) of the cast productunder analysis, and its Brinell hardness (HB).

This computing procedure comprises mainly an α' computing procedure540a, an m' computing procedure 540b, and a σB' computing procedure540c. In the example under discussion, these procedures are incorporatedas part of the tensile strength computing program 540 and they areexecuted in the order written.

The α computing procedure 540a is so specified as to express therelationship that the state of casting structure (FCD, FCV, FC) has withrespect to the sound velocity ratio ((V/Vm)) and the percent carboncontent (C).

The actual process of specifying the computing procedure of intereststarts with providing a number of cast products that resemble each otherin shape as closely as possible but which differ in percent carboncontent, and also providing at least one steel product. Then, the soundvelocity in these cast and steel products is measured with an apparatusfor ultrasonic measurement, and the sound velocity ratio between thecast and steel products is computed. Further, a direct method is used inaccordance with or as adapted from JIS specifications to measure thestate of casting structure, for instance, to check whether themorphology of graphite grains in each cast product is like flakes,vermicular, or spheroids (FC, FCV, FCD), or whether they are in a stateintermediate between these types. It should be noted that in order toensure agreement in the tendency of variations, the series ofdestructive measurements are desirably performed with the same apparatusfor ultrasonic measurement by the same inspector if possible.

Since this direct measurement is time-consuming, it is recommended thatanother series of measurements be performed in parallel on another groupof cast products and at least one steel product by another set ofapparatus for ultrasonic measurement and inspector so as to yield alarge number of measurement results.

It is also recommended that the index value for the state of castingstructure to be set be preferably one that is free of variablecomponents, by performing statistical processing such as decision makingby majority, averaging, local averaging, or regression analysis on theresults of the largest possible number of measurements.

The α' computing procedure 540a, as a specific example of the way tocompute the index value, proceeds as follows. First, on the basis of thesound velocity ratio ((V/Vm)) and the percent carbon content (C), thedensity p is computed by the equation:

    ρ=8.435-0.374×(C)

Then, the graphite area factor is computed by the equation:

    fg=1.095-0.1395×ρ

Finally, α' is computed by the equation:

    α'=((V/Vm).sup.2 ×(7.86/ρ)-1)/fg

It should be noted that the value 7.86 in the above equation isequivalent to the specific gravity of the steel product or the castingmatrix (base).

The thusly computed α' is the index value for the state of castingstructure that is based on the morphological classification of graphitegrains in the cast product (FC, FCV, FCD), and yet it is capable ofclearly identifying a state intermediate between those types (see thehorizontal axis α' of FIG. 5 and the distribution of data on themeasurement).

The m' computing procedure 540b is a procedure for computing thehardness coefficient m' from the index value α'. The hardnesscoefficient m' is an estimated value of hardness coefficient m, namely(tensile strength σB/hardness HB), and is determined from the indexvalue α' in accordance with the relationship between index value α' andhardness coefficient m that has been verified preliminarily on anexperimental basis. This relationship is shown in FIG. 5, with the indexvalue α' plotted on the horizontal axis and the hardness coefficient mon the vertical axis. Since there is a strong correlation between α' andm in FIG. 5, the relationship under consideration can be approximated bya kinked line or the like.

To give a specific example, the m' computing procedure 540b computes thehardness coefficient m' by the following criteria:

In the case of α'<3.15, computation is performed by the equation:

    m'=0.3920-0.0512×α';

in the case of 3.15≦α'≦4.00, computation is performed by the equation:

    m'=0.2306; and

in the case of 4.00<α', computation is performed by the equation:

    m'=0.3000-0.0173×α'.

The hardness coefficient m' that is computed by any of these equationsprovides a very good estimation of the actual hardness coefficient m.

The σB' computing procedure 540c is such that the tensile strength σB',as an estimated value of tensile strength σB, is computed from thehardness HB and hardness coefficient m' on the basis of the formula fordefining hardness coefficient m, namely, (m=σB/HB). Stated specifically,the procedure 540c computes the tensile strength σB' by the equationσB'=m'×HB.

The hardness coefficient m is introduced to replace the cumbersomemeasurement of the true percent spheroidicity of graphite by the easiermethod of computation or estimation on the basis of a tensile fracturetest. In the example under discussion, the role of this coefficient isexpanded on the basis of experimental results and, from the relationshipit has, the tensile strength σB' is computed in the manner describedabove.

With this configuration, the process of measuring the tensile strengthof a cast product starts with measuring the sound velocity in a steelproduct in mode 1 (the mode for setting the sound velocity in steel),followed by processing cast products successively in mode 2 (the modefor measuring the percent spheroidicity of graphite in castings).

Mode 1 is entirely the same as in the previous examples and, hence, neednot be described in detail. It should only be mentioned that in mode 1,the sound velocity in the steel product is set in area Vm.

In the next place, one of the cast products is used as specimen 1a.Then, the main program 550 is instructed to perform processing in mode2.

In the first step of this mode 2, the percent carbon content of the castspecimen 1a (which is known as one of the data for the castingoperation) is entered via keyboard 7 and set in area (C). If this dataentry is omitted, processing is performed on the assumption that thepercent carbon content is the same as that of the previous specimen.

In the subsequent second step, the main program 550 activates the soundvelocity measuring program 51, and the sound velocity in the castproduct being analyzed is stored in area V. If the specimen 1a is in theas-cast state, the value in area V may be left as it is. However, in adifferent case like the one where the specimen 1a is an annealed castproduct, 130 (m/s) is added as a correction value to the value of soundvelocity in area V; if the specimen 1a is a normalized cast product, 400(m/s) typically may be added. This correction helps further improve theprobability of the computed value.

Thereafter, in the third step, the main program 550 activates the soundvelocity normalizing program 512, and the sound velocity ratio ascomputed from the sound velocity (v) in the cast product being analyzedand the sound velocity (Vm) in steel is set in area (V/Vm).

Subsequently, in the fourth step, the Brinell hardness of the specimen1a as measured with a separate hardness tester is entered via keyboard 7and set in area HB. Then, the tensile strength computing program 540 isactivated by the main program 550.

The tensile strength computing program 540 executes the α' computingprocedure 540a, m' computing procedure 540b, and σB' computing procedure540c in that order, and computes the tensile strength on the basis ofthe sound velocity ratio (V/Vm), percent carbon content (C), and Brinellhardness (HB) that have been measured on the specimen 1a. The thuslycomputed tensile strength is stored in area σB' in RAM 6.

The fourth step is described below in detail. First, the index value α'is computed by the α' computing procedure 540a on the basis of the soundvelocity ratio (V/Vm) and percent carbon content (C). It should be notedhere that, if C is smaller than 9.0495-7.1189×(V/Vm) when computing α',the percent carbon content (C) must be replaced beforehand by the valueexpressed by the equation:

    8.7995-7.1189×(V/Vm)

This condition is applicable to the case where the cast product underanalysis corresponds to gray cast iron (FC), particularly to a typicalexample of it; this correction of C helps further improve theprobability of the computed value.

In the next place, the m' computing procedure 540b computes the hardnesscoefficient m' from the above α'. Then, except in the case of thealready evaluated gray cast iron which is mentioned above, the state ofcasting structure is classified on the basis of the value index α' orthe value of hardness coefficient m'. For example, if 0.27≦m', the castproduct under analysis is evaluated as being made of spheroidal graphitecast iron (FCD); in the case of 0.22≦m'<0.27, it is found to be made ofworm-like graphite cast iron (FCV); and if m'<0.22, it is found to bemade of flaky graphite cast iron (FCD).

Finally, the tensile strength (σB') is computed from the above-mentionedhardness coefficient m' and Brinell hardness (HB) by the σB' computingprocedure 540c.

The correspondence between the thusly computed tensile strength (σB')and the tensile strength (σB) that was measured directly by a tensiletest is shown in FIG. 6. As is clear from the FIG. 6 graph, the tensilestrength of castings that was computed by means of the apparatus of thepresent invention for ultrasonic measurement has an extremely highprobability. For instance, the estimated precision based on variance is2.15 (kgf/mm²). This is comparable to the estimated precision 1.93(kgf/mm²) for normalized or annealed steel products, which is usedextensively in designs using steel, whereas it is far better than theestimated precision 3.41 (kgf/mm²) for quenched and tempered steelproducts, which is also used extensively.

The tensile strength (σB') as well as the state of casting structure(FCD, FCV, FC) are displayed on CRT 8 by the main program 550 as theresult of measurement and analysis.

This ensures the following and other facts to be detected in a positiveand nondestructive manner: For example, heats that have been adjusted incomponents and the like with a view to producing spheroidal graphitecast iron having high tensile strength or toughness turn out to be shortof the intended tensile strength or, in certain cases, turn into CV castiron or flaky cast iron of lower strength as a result of delay inprocessing time or the like.

Thus, the tensile strength of castings can be measured or computed on asingle cast product with high reliability in a nondestructive and easymanner.

In addition, the sound velocity in the steel product need be measuredonly once and, hence, each of the remaining cast products may be usedsuccessively as specimen 1a for subsequent analyses of the state ofcasting structure and measurements of tensile strength on thoseproducts.

A fourth example of the present invention is described below withreference to the drawings. FIG. 7 is a block diagram of an apparatus forimplementing the method of the present invention for measuring thepercent elongation of castings, namely, an apparatus for ultrasonicmeasurement that measures the sound velocity in a cast specimen byultrasonic wave energy, and which computes automatically the percentelongation of that specimen.

The configuration of this apparatus is basically similar to that of thealready-described third example except that the tensile strengthcomputing program 540 in the third example is replaced by a new program542 and associated elements for computing the percent elongation.

The following explanation centers on the differences from the exampleshown in FIG. 4. The percent elongation computing program 542 issubstantially similar to the already-described tensile strengthcomputing program 540 as regards the basic configuration and thetechnical rationale; it is a sub-program that performs a specifiedmeasurement and a specified conversion process to compute the percentelongation of a cast product. Further, the specific configurations ofthe two programs are similar in that each has the α' computing procedure540a, m' computing procedure 540b, and σB' computing procedure 540c, andthat these procedures are executed in the order written.

However, the program 542 differs from the tensile strength computingprogram 540 in that it has an additional ε' computing procedure 540d forcomputing the percent elongation in the last step. Stated morespecifically, the program 542 performs a specified conversion processand computes the percent elongation of a cast product on the basis ofthree values: the value of sound velocity ratio in area (V/Vm), thevalue of percent carbon content in area C, and the value of Brinellhardness in area HB. The thusly computed elongation of the cast productis stored in area ε' in RAM 6.

The specified conversion process under consideration is anexperimentally predetermined computing procedure for computing thepercent elongation (ε') of the cast product on the basis of therelationship that its percent elongation (ε) has with respect to thesound velocity ratio ((V/Vm)) between the steel and the cast product,the percent carbon content (C) of the cast product under analysis, andits Brinell hardness (HB).

This computing procedure comprises mainly the α' computing procedure540a, m' computing procedure 540b, σB' computing procedure 540c, and theε' computing procedure 540d, and these procedures are executed in theorder written. All procedures except the ε' computing procedure 540dhave already been described above and discussion of them will not berepeated below.

The ε' computing procedure 540d is a procedure for computing the percentelongation ε from the index value α' and the estimated tensile strengthσB'. The percent elongation ε' is an estimated value of the actualpercent elongation ε, and is determined from the index value α' (whichhas been verified preliminarily on an experimental basis) and thetensile strength σB' (which has been computed on the basis of α') inaccordance with the relationship between the index value α', the tensilestrength σB', and the percent elongation ε which has been determined ina tensile test. This relationship is shown in FIG. 8, with the indexvalue α' being plotted on the horizontal axis and the product of tensilestrength σB' and percent elongation ε (σB'×ε) on the vertical axis.Since there is a strong correlation between α' and (σB'×ε) in FIG. 8,the relationship under consideration can be approximated by a kinkedline or the like.

To give a specific example, the ε' computing procedure 540d computes thepercent elongation ε' (in %) by the following criteria:

if α'<2.68, computation is performed by the equation:

    ε'=(3085-1035.6×α')σB'; and

if α'≦2.68, computation is performed by the equation:

    ε'=(676.3-137.2×α').

Obviously, if these equations are rewritten by expressing the tensilestrength σB' in terms of the above-described index value α', one canreadily obtain formulae for computing the percent elongation ε' solelyon the basis of the index value α'.

The thusly computed percent elongation ε' provides a very goodestimation of the actual percent elongation ε.

With this configuration, the process of measuring the percent elongationof a cast product starts with measuring the sound velocity in a steelproduct in mode 1 (the mode for setting the sound velocity in steel),followed by processing cast products successively in mode 2 (the modefor measuring the percent elongation of castings).

Again, details of the process are substantially similar to the case ofthe third example, and explanation of the overlapping portions will notbe repeated. The only difference from the third example is that thetensile strength of a cast product is not the sole factor to be computedin mode 2, and that the percent elongation (ε'), which is onecharacteristic value of the cast product, is also computed by thepercent elongation computing program 542 and outputted as the result ofmeasurement and analysis.

Further discussion is made of this point. In mode 2, the percentelongation computing program 542, like the tensile strength computingprogram 540, executes the α' computing procedure 540a, m' computingprocedure 540b, and σB' computing procedure 540c in that order, andcomputes the index value (α') and tensile strength (σB') from the soundvelocity ratio (V/Vm), percent carbon content (C), and Brinell hardness(HB) which have been measured on the specimen 1a. Subsequently, the ε'computing procedure computes the percent elongation (ε') from theabove-mentioned index value (α') and tensile strength (σB').

The correspondence between the thusly computed percent elongation (ε')and the percent elongation (ε) that was measured directly by a tensiletest is shown in FIG. 9. As is clear from the FIG. 9 graph, the percentelongation of castings that was computed by means of the apparatus ofthe present invention for ultrasonic measurement has a fairly highprobability.

This percent elongation (ε') as well as the state of casting structure(FCD, FCV, FC) are displayed on CRT 8 by the main program 550 as theresult of measurement and analysis.

This ensures the following and other facts to be detected in a positiveand nondestructive manner: For example, heats that have been adjusted incomponents and the like with a view to producing cast iron having highpercent elongation turn out to be short of the intended percentelongation as a result of mismatch with processing or the like.

Thus, the percent elongation of castings can be measured or computed ona single cast product with high reliability in a nondestructive and easymanner.

In addition, the sound velocity in the steel product need be measuredonly once and, hence, each of the remaining cast products may be usedsuccessively as specimen 1a for subsequent analyses of the state ofcasting structure and measurements of percent elongation on thoseproducts.

A fifth example of the present invention is described below withreference to the drawings. FIG. 10 is a block diagram of an apparatusfor ultrasonic measurement that is particularly advantageous for use oncopper-containing cast iron. For the especial purpose of assuringenhanced tensile strength, copper is sometimes contained in castings atsignificant levels of about 1% and, in the case of suchcopper-containing cast iron, the empirical formula to be used differsslightly from the case just described above, and is necessary to makecorrections in accordance with the present copper content.

The configuration of the apparatus under consideration is basicallysimilar to that of the already-described fourth example, except that theε' computing procedure in the percent elongation computing program usedin the fourth example is replaced by a new procedure and associatedelements for computing ε".

The following explanation centers on the differences from the exampleshown in FIG. 7. The percent elongation computing program 541 issubstantially similar to the already-described percent elongationcomputing program 540 as regards the basic configuration and thetechnical rationale; it is a sub-program that performs a specifiedmeasurement and a specified conversion process to compute the percentelongation of a cast product. However, the program 541 differs from thepercent elongation computing program 540 in that the cast product to bemeasured is limited to copper-containing cast iron, and in that thepercent elongation of the cast product is computed not simply from thevalues of sound velocity ratio in area (V/Vm), percent carbon content inarea C, and Brinell hardness in area HB, but from the combination ofthese values with the percent copper content (in %). The thusly computedpercent elongation of the cast product is stored in area ε" in RAM 6.

The specified conversion process under consideration is anexperimentally predetermined computing procedure for computing thepercent elongation (ε") of the cast product on the basis of therelationship that its percent elongation (ε) has with respect to thesound velocity ratio ((V/Vm)) between the steel and cast product, thepercent carbon content (C) of the cast product under analysis, itsBrinell hardness (HB), and its percent copper content (Cu).

This computing procedure comprises mainly the already-described α'computing procedure 540a, m' computing procedure 540b, and σB' computingprocedure 540c, as well as the new procedure 541d for computing ε". Inthe example under discussion, these procedures are incorporated as partof the percent elongation computing program 541 and they are executed inthe order written.

Explanation of the α' computing procedure 540a, m' computing procedure540b, and σB' computing procedure 540c is not repeated here but, asalready mentioned, these programs compute α', m', and σB', respectively,from the sound velocity ration ((V/Vm)), percent carbon content (C), andBrinell hardness (HB).

The ε" computing procedure 541d is a procedure by which the percentelongation ε" as an estimated value of the actual percent elongation εis computed from the index value α', estimated tensile strength σB', andpercent copper content (Cu) To determine the percent elongation ε", thepercent elongation ε' in the aforementioned example which has beencomputed from the index value α' and the estimated tensile strength σB'is first corrected by the percent copper content (Cu) to yield the value(ε'/(2×Cu)), and this value (ε'/(2×Cu)) is fitted into the relation ithas with respect to the percent elongation ε, which was determined in atensile test. This relationship is shown in FIG. 11, with the value(ε'/(2×Cu)) being plotted on the horizontal axis and the percentelongation ε on the vertical axis. Since there is a strong correlationbetween (ε'/(2×Cu)) and ε in FIG. 11, the relationship underconsideration can be approximated by a kinked line or the like.

To give a specific example, the ε" computing procedure 541d expressesthe percent elongation ε' in terms of the index value α' and the tensilestrength σB', and determines ε" from the index value α', tensilestrength σB, and percent carbon content (Cu in %) by the followingcriteria:

If α'<2.68, computation is performed by the equation:

    ε"=(0.165×(3085-1035.6×α')/(σB'×U))+2.3; and

if α'≧2.68, computation is performed by the equation:

    ε"=(0.165×(676.3-137.2×α')/(σB'×U))+2.3.

Thus, the percent elongation ε" is computed (in %).

Obviously, if the equations set forth above are rewritten by expressingthe tensile strength σB' in terms of the above-described index value α',one can readily obtain formulae for computing the percent elongation ε"solely on the basis of the index value α' and the percent copper content(Cu).

The thusly computed percent elongation ε" provides a fairly goodestimation of the actual percent elongation ε for the copper-containingcast iron (see FIG. 12).

With this configuration, the process of measuring the percent elongationof a cast product starts with measuring the sound velocity in a steelproduct in mode 1 (the mode for setting the sound velocity in steel),followed by processing cast products successively in mode 2 (the modefor measuring the percent elongation of castings).

Again, details of the process are substantially similar to the case ofthe already-described examples, and explanation of the overlappingportions will not be repeated. The only difference from thealready-described examples is that, besides inputting the percent carboncontent of the cast specimen 1a, its percent copper content (which isknown as one of the data for the casting operation) is entered viakeyboard 7 and set in area (Cu). If this data entry is omitted,processing is performed on the assumption that the percent coppercontent is the same as that of the previous specimen.

Thereafter, the percent elongation that has been computed by the percentelongation computing program 541 is stored in area ε" in RAM 6, and thispercent elongation (ε") is displayed on CRT 8 by the main program 550 asthe result of measurement and analysis.

This ensures the following and other facts to be detected in a simpleand nondestructive manner: For example, heats that have been adjusted incomponents and the like by adding copper with a view to producing castiron having high tensile strength turn out to be short of the intendedpercent elongation as a result of mismatch with processing or the like.

Thus, the percent elongation of castings can be measured or computed ona single cast product with high reliability in a nondestructive and easymanner, even if the cast product is copper-containing cast iron.

It should be noted that in all of the examples discussed hereinabove,the reference value for normalizing the sound velocity is desirablytaken on a steel product that is in the same state as the so-called"casting matrix (base)"; however, other metals may be used as long asconsistency is insured between the operation of preparing the computingprocedures and that of actual measurements.

It should also be noted in the case of basing on the sound velocityrather than on the sound velocity ratio, namely, in the case whereanalyses or measurements are conducted on the basis of the percentcarbon content, hardness, and sound velocity (or a combination of thesewith the percent copper content), the sound-velocity-in-steel settingprogram 511, the sound velocity normalizing program 512, etc. areunnecessary, and the above-described examples will apply as such if onlythe steel-related processing and the like are eliminated; hence, adetailed explanation of this alternative case is omitted.

Industrial Applicability

As described on the foregoing pages, the method and apparatus of thepresent invention for ultrasonic measurement are suitable for use oncastings if one wants to determine reliable physical characteristicvalues (e.g. percent spheroidicity of graphite, tensile strength, andpercent elongation) and state analysis values in a nondestructive andsimple manner.

I claim:
 1. In a method of ultrasonic measurement in which the velocityof propagation of an ultrasonic wave in a cast specimen is measured anda physical characteristic value of said specimen that has a physicalcorrelation with said ultrasonic wave propagation velocity wave isdetermined, the improvement comprising the steps of:determining avelocity ratio between the ultrasonic wave propagation velocity in saidspecimen and the velocity of ultrasonic wave propagation in a givenmetal that corresponds to said specimen; and converting the velocityratio into the physical characteristic value, thereby determining saidphysical characteristic value of said specimen.
 2. A method ofultrasonic measurement according to claim 1, wherein said convertingstep converts the velocity ratio into the physical characteristic valueaccording to an empirical formula associated with the velocity ratio. 3.In an apparatus for ultrasonic measurement which measures the velocityof propagation of an ultrasonic wave in a cast specimen and determines aphysical characteristic value of said cast specimen that has a physicalcorrelation with said ultrasonic wave velocity of propagation, theimprovement comprising:processing means by which a first physicalquantity is processed to determine a second physical quantity that isequivalent to said physical characteristic value of said cast specimen;reference ultrasonic wave propagation velocity generating means by whichthe ultrasonic wave velocity of propagation as attained by ultrasonicmeasurement on a steel specimen is generated as a reference ultrasonicwave propagation velocity; and characteristic value generating meanswhich determines said second physical quantity by said processing meansand which generates the thus determined second physical quantity as saidphysical characteristic value of said cast specimen, the ratio betweenthe ultrasonic wave propagation velocity in said cast specimen asattained by ultrasonic measurement on said specimen and said referenceultrasonic wave propagation velocity being an equivalent of said firstphysical quantity; wherein the ultrasonic wave propagation velocity inthe cast specimen and the ultrasonic wave propagation velocity in thesteel specimen are both attained by measurement with the same apparatusfor ultrasonic measurement, and wherein said processing means possesseseither of a characteristic function or a table or a processing procedurethat represents the correlation between said first physical quantity andsaid second physical quantity based on measurements of said ultrasonicwave propagation velocity in said cast specimen and of said physicalcharacteristic value, which have been made previously on a plurality ofsamples of said cast specimen, said physical characteristic value havingbeen measured directly on said cast specimen with a measuring apparatusother than the one for ultrasonic measurement.
 4. An apparatus forultrasonic measurement according to claim 3, wherein said processingmeans includes an empirical formula program.
 5. In a method ofultrasonic measurement in which the velocity of propagation of anultrasonic wave in a cast specimen is measured and the state of castingstructure of said cast specimen that has a physical correlation withsaid ultrasonic wave propagation velocity is analyzed, the improvementcomprising the steps of:ascertaining the percent carbon content orcarbon equivalent of said cast specimen and the velocity of propagationof ultrasonic wave in said specimen; and attaining an analytical valueequivalent to said state of casting structure from the percent carboncontent or carbon equivalent and ultrasonic wave propagation velocity insaid cast specimen, whereby the state of casting structure in said castspecimen is analyzed in terms of said analytical value.
 6. A method ofultrasonic measurement according to claim 5, wherein said attaining stepattains the analytical value in accordance with an empirical formula. 7.In an apparatus for ultrasonic measurement which measures the velocityof propagation of an ultrasonic wave in a cast specimen with a knownpercent carbon content or carbon equivalent and analyzes the state ofcasting structure in said cast specimen, the improvementcomprising:processing means by which a first physical quantity and asecond physical quantity are processed to determine a third physicalquantity that is equivalent to said state of casting structure; andstate evaluating means which determines said third physical quantity bysaid processing means, provided that the ultrasonic wave propagationvelocity in said cast specimen as attained by ultrasonic measurement onsaid cast specimen is an equivalent of said first physical quantity, andthat said percent carbon content or said carbon equivalent is anequivalent of said second physical quantity, said state evaluating meansevaluating said state of casting structure in accordance with the thuslydetermined third physical quantity;wherein said empirical formulaprogram possesses either a characteristic function, a table or aprocessing procedure that represents the correlation between said firstphysical quantity, said second physical quantity, and said thirdphysical quantity based on measurements of said ultrasonic wavepropagation velocity in said cast specimen, of said percent carboncontent or carbon equivalent and of said state of casting structurewhich have been measured previously on a plurality of samples of saidcast specimen, said state of casting structure having been measureddirectly on said cast specimen with a measuring apparatus other than theone for ultrasonic measurement.
 8. An apparatus for ultrasonicmeasurement according to claim 7, wherein said processing means includesan empirical formula program.
 9. In an apparatus for ultrasonicmeasurement which measures the velocity of propagation of an ultrasonicwave in a cast specimen with a known percent carbon content or carbonequivalent and analyzes the state of casting structure in said castspecimen, the improvement comprising:processing means by which a firstphysical quantity and a second physical quantity are processed todetermine a third physical quantity that is equivalent to said state ofcasting structure; reference ultrasonic wave propagation velocitygenerating means by which the ultrasonic wave propagation velocity asattained by ultrasonic measurement on a steel specimen is generated as areference ultrasonic wave propagation velocity; state evaluating meanswhich determines said third physical quantity by said processing means,provided that the velocity ratio between the ultrasonic wave propagationvelocity in said cast specimen as attained by ultrasonic measurement onsaid cast specimen and said reference ultrasonic wave propagationvelocity is said first physical quantity, and that said percent carboncontent or said carbon equivalent is an equivalent of said secondphysical quantity, said state evaluating means evaluating said state ofcasting structure in accordance with the thusly determined thirdphysical quantity; andwherein said processing means possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between said first physical quantity, saidsecond physical quantity, and said third physical quantity based onmeasurements of said ultrasonic wave propagation velocity, of saidpercent carbon content or said carbon equivalent, and said state ofcasting structure which have been measured previously on a plurality ofsamples of said cast specimen, said state of casting structure havingbeen measured directly on said cast specimen with a measuring apparatusother than the one for ultrasonic measurement.
 10. An apparatus forultrasonic measurement according to claim 9, wherein said processingmeans includes an empirical formula program.
 11. A method of ultrasonicmeasurement in which the velocity of propagation of an ultrasonic wavein a cast specimen is measured and the tensile strength of said castspecimen is determined, comprising the steps of:attaining the percentcontent or carbon equivalent and the hardness of said specimen, as wellas the ultrasonic wave propagation velocity in said cast specimen; anddetermining the tensile strength of said specimen from the percentcarbon content or carbon equivalent, and from the hardness of said castspecimen and the ultrasonic wave propagation velocity in said castspecimen.
 12. A method of ultrasonic measurement according to claim 11,wherein said determining step determines the tensile strength inaccordance with an empirical formula, by which the tensile strength isattained from the percent carbon content or carbon equivalent, and fromthe hardness of the cast specimen and the ultrasonic wave propagationvelocity in said cast specimen.
 13. An apparatus for ultrasonicmeasurement which measures the velocity of propagation of an ultrasonicwave in a cast specimen with a known percent carbon content or carbonequivalent and determines the tensile strength of said cast specimen,comprising:processing means by which a first physical quantity, a secondphysical quantity, and a third physical quantity are processed todetermine a fourth physical quantity that is equivalent to said tensilestrength; and tensile strength computing means which determines saidfourth physical quantity by said processing means, provided that theultrasonic wave propagation velocity in said cast specimen as attainedby ultrasonic measurement on said cast specimen is an equivalent of saidfirst physical quantity, said percent carbon content or carbonequivalent is an equivalent of said second physical quantity, and thehardness of said cast specimen is an equivalent of said third physicalquantity, said tensile strength computing means outputting the thuslydetermined fourth physical quantity as the value of said tensilestrength;wherein said processing means possesses either a characteristicfunction, a table, or a processing procedure that represents thecorrelation between said first physical quantity, said second physicalquantity, said third physical quantity, and said fourth physicalquantity based on measurements of said ultrasonic wave propagationvelocity, of said percent carbon content or carbon equivalent, of saidhardness, and of said tensile strength which have been measuredpreviously on a plurality of samples of said cast specimen, said tensilestrength having been measured on said cast specimen by a direct means oftensile strength measurement other than the apparatus for ultrasonicmeasurement.
 14. An apparatus for ultrasonic measurement according toclaim 13, wherein said processing means includes an empirical formulaprogram.
 15. An apparatus for ultrasonic measurement which measures thevelocity of propagation of an ultrasonic wave in a cast specimen with aknown percent carbon content or carbon equivalent and determines thetensile strength of said cast specimen, comprising:processing means bywhich a first physical quantity, a second physical quantity, and a thirdphysical quantity are processed to determine a fourth physical quantitythat is equivalent to said tensile strength; reference ultrasonic wavepropagation velocity generating means by which the ultrasonic wavepropagation velocity as attained by ultrasonic measurement on a steelspecimen is generated as a reference ultrasonic wave propagationvelocity; and tensile strength computing means which determines saidfourth physical quantity by said processing means, provided that thevelocity ratio between the ultrasonic wave propagation velocity in saidcast specimen as attained by ultrasonic measurement on said castspecimen and said reference ultrasonic wave propagation velocity is anequivalent of said first physical quantity, said percent carbon contentor said carbon equivalent is an equivalent of said second physicalquantity, and the hardness of said cast specimen is an equivalent ofsaid third physical quantity, said tensile strength computing meansoutputting the thusly determined fourth physical quantity as the valueof said tensile strength;wherein said processing means possesses eithera characteristic function, a table, or a processing procedure thatrepresents the correlation between said first physical quantity, saidsecond physical quantity, said third physical quantity, and said fourthphysical quantity based on measurements of said ultrasonic wavepropagation velocity, of said percent carbon content or carbonequivalent, of said hardness, and of said tensile strength which havebeen measured previously on a plurality of samples of said castspecimen, said tensile strength having been measured on said castspecimen by a direct means of tensile strength measurement other thanthe apparatus for ultrasonic measurement.
 16. An apparatus forultrasonic measurement according to claim 15, wherein said processingmeans includes an empirical formula program.
 17. An apparatus forultrasonic measurement which measures the velocity of propagation of anultrasonic wave in a specimen of cast iron with a known percent carboncontent or carbon equivalent and measures the tensile strength of saidcast iron specimen, comprising:tensile strength computing means forcomputing the equation ρ=8.435-0.374×C; a second intermediate value fgby the equation fg=1.095-0.1395×ρ; the equation α'=(R⁻² ×(7.86/ρ)-1)/fg;one of the empirical formulae m'=0.3920-0.0512×α', m'=0.2306 andm'=0.3000-0.0173×α' selectively under specified conditions; and theequation m'×H, wherein C is a first variable, R is a second variable,and H is a third variable; and reference ultrasonic wave propagationvelocity setting means by which the ultrasonic wave propagation velocityin a steel specimen as attained by ultrasonic measurement on said steelspecimen is outputted as a reference ultrasonic wave propagationvelocity;wherein said tensile strength computing means computes thetensile strength of said cast iron specimen by said equations, providedthat the carbon percent content or carbon equivalent of said cast ironspecimen is the value of said first variable C, that the velocity ratiobetween the ultrasonic wave propagation velocity in said cast ironspecimen as attained by ultrasonic measurement on said cast ironspecimen and said reference ultrasonic wave propagation velocity is thevalue of said second variable R, and that the hardness of said cast ironspecimen is the value of said third variable H.
 18. A method ofultrasonic measurement in which the velocity of propagation of anultrasonic wave in a cast specimen is measured and the percentelongation of said cast specimen is determined, comprising the stepsof:determining the percent carbon content or carbon equivalent and thehardness of said cast specimen, as well as the ultrasonic wavepropagation velocity in said cast specimen; and determining the percentelongation of said cast specimen from the percent carbon content orcarbon equivalent and the hardness of said cast specimen and theultrasonic wave propagation velocity in said cast specimen.
 19. Anmethod of ultrasonic measurement according to claim 18, wherein saidstep of determining the percent elongation is performed in accordancewith an empirical formula, by which the percent elongation is attainedfrom the percent carbon content or carbon equivalent, and the hardnessof the cast specimen and the ultrasonic wave propagation velocity insaid cast specimen.
 20. An apparatus for ultrasonic measurement whichmeasures the velocity of propagation of an ultrasonic wave in a castspecimen with a known percent carbon content or carbon equivalent anddetermines measures the percent elongation of said cast specimen,comprising:processing means by which a first physical quantity, a secondphysical quantity, and a third physical quantity are processed todetermine a fourth physical quantity that is equivalent to said percentelongation; and percent elongation computing means which determines saidfourth physical quantity by said processing means, provided that theultrasonic wave propagation velocity in said specimen as attained byultrasonic measurement on said cast specimen is an equivalent of saidfirst physical quantity, said percent carbon content or said carbonequivalent is an equivalent of said second physical quantity, and thehardness of said cast specimen is an equivalent of said third physicalquantity, said percent elongation computing means outputting the thuslydetermined fourth physical quantity as the value of said percentelongation;wherein said processing means possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between said first physical quantity, saidsecond physical quantity, said third physical quantity, and said fourthphysical quantity based on said ultrasonic wave propagation velocity, ofsaid percent carbon content or carbon equivalent, of said hardness, andof said percent elongation which have been measured previously on aplurality of samples of said cast specimen, said percent elongationhaving been measured on said cast specimen by a direct means of percentelongation measurement other than the apparatus for ultrasonicmeasurement.
 21. An apparatus for ultrasonic measurement according toclaim 20, wherein said processing means includes an empirical formulaprogram.
 22. An apparatus for ultrasonic measurement which measures thevelocity of propagation of an ultrasonic wave in a cast specimen with aknown percent carbon content or carbon equivalent and determines thepercent elongation of said cast specimen, comprising:processing means bywhich a first physical quantity, a second physical quantity, and a thirdphysical quantity are processed to determine a fourth physical quantitythat is equivalent to said percent elongation; reference ultrasonic wavepropagation velocity generating means by which the ultrasonic wavepropagation velocity as attained by ultrasonic measurement on a steelspecimen is generated as a reference ultrasonic wave propagationvelocity; and percent elongation computing means which determines saidfourth physical quantity by said processing means, provided that thevelocity ratio between the ultrasonic wave propagation velocity in saidcast specimen as attained by ultrasonic measurement on said castspecimen and said reference ultrasonic wave propagation velocity is anequivalent of said first physical quantity, said percent carbon contentor said carbon equivalent is an equivalent of said second physicalquantity, and the hardness of said cast specimen is an equivalent ofsaid third physical quantity, said percent elongation computing meansoutputting the thusly determined fourth physical quantity as the valueof said percent elongation;wherein said processing means possesseseither a characteristic function, a table, or a processing procedurethat represents the correlation between said first physical quantity,said second physical quantity, said third physical quantity, and saidfourth physical quantity based on measurements of said ultrasonic wavepropagation velocity, of said percent carbon content or carbonequivalent, of said hardness, and of said percent elongation which havebeen measured previously on a plurality of samples of said castspecimen, said percent elongation having been measured on said castspecimen by a direct means of percent elongation measurement other thanthe apparatus for ultrasonic measurement.
 23. An apparatus forultrasonic measurement according to claim 22, wherein said processingmeans includes an empirical formula program.
 24. An apparatus forultrasonic measurement which measures the velocity of propagation of anultrasonic wave in a specimen of cast iron with a known percent carboncontent or carbon equivalent, and determines the percent elongation ofsaid cast iron specimen, comprising:percent elongation computing meansfor computing the equation ρ=8.435-0.374×C; the equationfg=1.095-0.1395×ρ; the equation α'=(R⁻² ×7.86/ρ)-1)/fg; one of theempirical formulae m'=0.3920-0.0512×α', m'=0.2306, andm'=0.3000-0.0173×α', which are applied selectively under specifiedconditions; the equation m'×H; and one of ε'=3085-1035.6×α')/σB' andε'=(676.3-137.2×α')/σB' which are applied selectively under specifiedconditions; wherein C is a first variable, R is a second variable, and His a third variable; and reference ultrasonic wave propagation velocitysetting means by which the ultrasonic wave propagation velocity in asteel specimen as attained by ultrasonic measurement on said steelspecimen is outputted as a reference ultrasonic wave propagationvelocity;wherein said percent elongation computing means computes thepercent elongation of said cast specimen by said equations, providedthat the carbon content or carbon equivalent of said cast specimen isthe value of said first variable C, that the velocity ratio between theultrasonic wave propagation velocity in said cast specimen as attainedby ultrasonic measurement on said cast specimen and said referenceultrasonic wave propagation velocity is the value of said secondvariable R, and that the hardness of said cast specimen is the value ofsaid third variable H.
 25. A method of ultrasonic measurement in whichthe velocity of propagation of an ultrasonic wave in a cast specimen ismeasured and the percent elongation of said cast specimen is determined,said cast specimen being a copper-containing cast iron, comprising thesteps of:attaining the percent copper content, the percent carboncontent or carbon equivalent, and the hardness of said cast specimen, aswell as the ultrasonic wave propagation velocity in said cast specimen;and determining the percent elongation of said cast specimen from thepercent copper content, the percent carbon content or carbon equivalent,and the hardness of said cast specimen and the ultrasonic wavepropagation velocity in said cast specimen.
 26. A method of ultrasonicmeasurement according to claim 25, wherein said determining stepdetermines the percent elongation in accordance with an empiricalformula, by which the percent elongation is attained from the percentcopper content, percent carbon content or carbon equivalent, and fromthe hardness of the cast specimen and the ultrasonic wave propagationvelocity in said cast specimen.
 27. An apparatus for ultrasonicmeasurement which measures the velocity of propagation of an ultrasonicwave in a specimen formed of a copper-contained cast iron with knownpercent copper and carbon content or carbon equivalent, and determinesthe percent elongation of said specimen, comprising:processing means bywhich a first physical quantity, a second physical quantity, a thirdphysical quantity, and a fourth physical quantity are processed todetermine a fifth physical quantity that is equivalent to said percentelongation; and percent elongation computing means which determines saidfifth physical quantity by said processing means, provided that theultrasonic wave propagation velocity in said specimen as attained byultrasonic measurement on said specimen is an equivalent of said firstphysical quantity, said percent carbon content or said carbon equivalentis an equivalent of said second physical quantity, the hardness of saidspecimen is an equivalent of said third physical quantity, and saidpercent copper content is an equivalent of said fourth physicalquantity, said percent elongation computing means outputting the thuslydetermined fifth physical quantity as the value of said percentelongation;wherein processing means possesses either a characteristicfunction, a table, or a processing procedure that represents thecorrelation between said first physical quantity, said second physicalquantity, said third physical quantity, said fourth physical quantity,and said fifth physical quantity based on measurements of saidultrasonic wave propagation velocity, of said hardness, of said percentcarbon content or carbon equivalent, of said percent copper content, andof said percent elongation which have been measured previously on aplurality of samples of said specimen, said percent elongation havingbeen previously measured on said specimen by a direct means of percentelongation measurement other than the apparatus for ultrasonicmeasurement.
 28. An apparatus for ultrasonic measurement according toclaim 27, wherein said processing means includes an empirical formulaprogram.
 29. An apparatus for ultrasonic measurement which measures thevelocity of propagation of an ultrasonic wave in a copper-containingcast iron specimen with known percent copper and carbon content orcarbon equivalent, and determines the percent elongation of saidcopper-containing cast iron specimen, comprising:processing means bywhich a first physical quantity, a second physical quantity, a thirdphysical quantity, and a fourth physical quantity are processed todetermine a fifth physical quantity that is equivalent to said percentelongation; reference ultrasonic wave propagation velocity generatingmeans by which the ultrasonic wave propagation velocity as attained byultrasonic measurement on a steel specimen is generated as a referenceultrasonic wave propagation velocity; and percent elongation computingmeans which determines said fifth physical quantity by said processingmeans, provided that the velocity ratio between the ultrasonic wavepropagation velocity in said copper-containing cast iron specimen asattained by ultrasonic measurement on said specimen and said referenceultrasonic wave propagation velocity is an equivalent of said firstphysical quantity, said percent carbon content or said carbon equivalentis an equivalent of said second physical quantity, the hardness of saidcopper-containing cast iron specimen is an equivalent of said thirdphysical quantity, and said percent copper content is an equivalent ofsaid fourth physical quantity, said percent elongation computing meansoutputting the thusly determined fifth physical quantity as the value ofsaid percent elongation;wherein said processing means possesses either acharacteristic function, a table, or a processing procedure thatrepresents the correlation between said first physical quantity, saidsecond physical quantity, said third physical quantity, said fourthphysical quantity, and said fifth physical quantity based onmeasurements of said ultrasonic wave propagation velocity, of saidpercent carbon content or carbon equivalent, of said hardness, of saidpercent copper content, and of said percent elongation which have beenmeasured previously on a plurality of samples of said copper-containingcast iron specimen, said percent elongation having been measured on saidcopper-containing cast iron specimen by a direct means of percentelongation measurement other than the apparatus for ultrasonicmeasurement.
 30. An apparatus for ultrasonic measurement according toclaim 29, wherein said processing means includes an empirical formulaprogram.
 31. An apparatus for ultrasonic measurement which measures thevelocity of propagation of an ultrasonic wave in a specimen ofcopper-containing cast iron with known percent copper and carbon contentor carbon equivalent, and determines the percent elongation of saidcopper-containing cast iron specimen, comprising:percent elongationcomputing means for computing the equation ρ=8.435-0.374×C; the equationfg=1.095-0.1395×ρ; the equation α'=(R⁻² ×(7.86/ρ)-1)/fg; one of theempirical formulae m'=0.3920-0.0512×α', m'=0.2306, andm'-0.3000-0.0173×α' which are applied selectively under specifiedconditions; the equation m'×H; and any one of empirical formulaeε"=(0.165×(3085-1035.6×α')/(σB' ×Cu))+2.3 andε"=(0.165×676.3-137.2×α')/(σB'×Cu))+2.3 which are applied selectivelyunder specified conditions; wherein C is a first variable, R is a secondvariable, H is a third variable, and Cu is a fourth variable; andreference ultrasonic wave propagation velocity setting means by whichthe velocity of propagation of an ultrasonic wave in a steel specimen asattained by ultrasonic measurement on said steel specimen is outputtedas a reference ultrasonic wave propagation velocity;wherein said percentelongation computing means computes the percent elongation of saidcopper-containing cast iron specimen by said equations, provided thatthe carbon content or carbon equivalent of said copper-containing castiron specimen is the value of said first variable C, that the velocityratio between the ultrasonic wave propagation velocity in saidcopper-containing cast iron specimen as attained by ultrasonicmeasurement on said copper-containing cast iron specimen and saidreference ultrasonic wave propagation velocity is the value of saidsecond variable R, that the hardness of said copper-containing cast ironspecimen is the value of said third variable H, and that the percentcopper content of said copper-containing cast iron specimen is the valueof said fourth variable Cu.